Spot-welding machine



May 5, 1925.

H. GEISENHONER SPOT WELDING momma Filed Oct. 20, 1923 n..." "Milli I r I" I IN Ihventor: Henry Geisenhnefi Pram-.1 May s, "1925.

UNITED STATES PATENT OFFICE.

may noun, or scnnnncrany, new YORK, nssrcnon no G- nuc- TBIGOO IPANY, A CORPORATION OF NEW YORK.

SPOT-WELDING MACHINE.

Application fled October 20, 1923. Serial No. 869,888.

To all whom it may concern;

Be it known that I, HENRY Gnisnnnonnn, a citizen of the United States, residin at Schenectady, county of Schenectady, tate 6 of New York, have invented certain new and useful Improvements in Spot-Welding v Machines, of which the following is a specification.

My invention relates to electric welding 10 and particularly to machines for spot welding plates or other structural parts and an ob ect of In invention is to provide an imroved macliine for this purpose which shall simple and rugged in construction and 15 efiicient in operation.

My invention will be better understood from the following descri tion and accompanying drawing, in whic Fig.1 is a side elevation of a machine embodying my invention; Fig. 2 is a fragmentary top view of the same showing the slidable electrode carrier; Fig. 3 is a top view of the transformer and attachedleads forming a part of the machine; Fig. 4 is a circuit diagram of the arrangement shown in Fig. 1; Fig.-

5-is fra entary side elevation of a modified form machine; Fig. 6 is a detail of the same; and Fig. 7 is a circuit diagram of the modified form.- a 7 Referring first to Fig. 1, the frame 1 has a vertically slidable head or electrode carrier 2 mounted thereon, which carrier is provided with a rack 3 meshing with a gear segment 4 on the end of a lever 5. A link 6 35 connects the lever with a foot lever 7, a spring 8 normally holding the lever 7 and connected parts in the position illustrated by Fig. 1. The frame 1 supports two fixed e ectrodes 9 see Fig. 4), the one arranged behind the ot er, as seen in Fig. 1, and cooperating with this pair of electrodes is a movable pair of electrodes 10 carried by the carrier 2 and having a limited verticalmovement relative thereto. Each electrode 45 10 has secured to it a guide rod 11 surrounding which is a comparatively stifi' coil spring 12. These springs eing compressed between theicarrier 2 and a nut'13 on each rod 11 serve to eallmlize the pressure exerted on the work by are supplied with the necessary current. The

0 two movable electrodes, thereby compensating for any irregularity there- Located within the throat of the frame 1 is a transformer from which the electrodes 55 core 15 of this transformer carries a rimary winding 16 and a secondary winding 17, the latter comprising, in the form illustrated, a single turn of ribbon conductor. The two ends of the secondary winding are connected respectively with the central portions of connectors 18 and 19 whose ends in turn connect with' four leads 20 extending to the electrodes. The leads 20 are arranged in two spaced pairs as shown, the two leads comprising a pair being arranged one above the other and separated only by a thin strip of insulation. For the sake of greater clearness in illustrating these connections, connector 18 is shown positioned slightly forward of connector 19 and connected tothe secondary winding by a -spacer 21.

The leads and connectors are so arranged that the two leads which lie adjacent each other carry current in opposite directions and the two leads attached to-a single connector connect with diagonally opposite electrodes.

The manner of connecting the electrodes to the secondary is clearly shown by the 80 diagram comprising Fig. 4. It will thus be seen that I connect the single secondary winding to supply current in parallel to the two circuits including the two pairs of cooperating electrodes and since the leads forming a pair lie close to each other and carry current in opposite directions the reactances of the two circuits neutralize each other. l

The primary winding 16 of the transformer is connected to be controlled by a switch 24 which is operated by a link connection 25 with the foot lever 7. The switch 24 is so adjusted that the circuit is not closed until after the lever 7 has been moved a suflicient distance to firmly clamp the work between the electrodes and upon the release of the foot lever the switch will open before the pressure is relieved.

It has been found that Where a single 100 secondary is connected to supply current in parallel to "two sets of welding electrodes any appreciable difference in the amount of scale, rust or other matter on the work to be welded affects the distribution of current taken by the two sets of electrodes.

The voltage applied to the electrodes being electrodes'that the conductors carrying ourrent in opposite directions are grouped in pairs and lie closely adjacent each other as has already been described above. Further equalization of the currents in the two parallel circuits may be effected by 'surrounding a pair of leads carrying current in opposite irections by a laminated ring as shown in Fig. 7 in connection with the modification now to be described.

In the modified form illustrated by Fig. 5, the two pairs of electrodes are arranged in a slidable carrier 28 but with the one in front of the other instead of side by side as in Fig. 1. In both forms it is obviously necessary to insulate one or the other electrode and its guide rod 11 from the carrier. This construction is shown for example in Fi 6 andis applicable to both forms. In t at figure it will be seen that the electrodes 10 are carried by plungers 29 having collars 30, which plungers slide in insulated bearings 31 in the carrier 28. lhe upper end of the rod '11 and the nut 32 are also insulated from the carrier 28 by bushings and washers as shown. In the case. of the modified form illustrated by Fig. 5, the leads 2O connecting with the forward pair of electrodes are necessarily longer than. the two others. The effect of the resulting increase in impedance of the two longer leads is partly if not entirely compensated by so adjusting the parts that the forward electrodes will engage the work first and exert a greater pressure thereon.. "Fi 5 illustrates the position of the parts w en the. frame 2 has been depressed an amount suflicient to cause the forward pair of electrodes only to engage and begin to compress a pair of plates 34 to be welded. Further movement of the foot lever 7 causes the switch 24 to close the riinary circuit and then the rear, pair of e ectrodes to engage and compress the plates. The increase in pressure between the two forward electrodes naturally decreases the resistance therebetween, other conditions being the same. The earlier contact of these electrodes also provides a slightly longer heating interval. As a further means of maintaining an equal current flow through the two pairs of electrodes, a laminated core 35- may be employed to surround one or the other pair of leads 20 as shown for example in Fig. 7.

While I have described certain embodiments of my invention, I do not wish to be limited to the particular forms shown and having a secondary winding for supplying I current to said electrodes and pairs of leads for connecting said secondary winding with said two pairs of electrodes in arallel relation, the leads forming each pair being respectively connected to opposite terminals of said secondary winding.

2. A spot welding machine comprising a frame, two pairs of relatively movable electrodes carried thereby and adapted simultaneously to produce a pair of spaced spot welds, a transformer having a secondary winding for supplying current to said electrodes, and a separate lead for each of said electrodes, said leads being arranged in closely adjacent pairs, each comprising a positive-and a negative lead and connected to said secondary winding to provide two circuits in parallel.

3. A spot welding machine comprising a frame having opposed jaws an inner pair and an outer pair of electro es for simultaneously producing a pair of spaced spot welds, a transformer, leads extendin therefrom along said jaws to said electro es and forming therewith two circuits connected in parallel, and means for pressing together said electrodes, said means bein constructed to press together the electro es forming said outer pair with a greater pressure than the electrodes forming said inner pair.

4. A spot welding machine comprising a frame having opposed jaws, an inner pair and an outer air of electrodes for simultaneously pro ucing a pair of s aced spot welds, a transformer, leads exten ing therefrom along said jaws to said electrodes and forming therewith two circuits connected in parallel, and means for pressing together said electrodes to causethe electrodes forming the outer pair to engage the work before the electrodes forming the inner pair.

5. A spot welding machine comprising a frame having opposed jaws, an electrode carrier slidably mounted on the upper of said jaws, electrodes mounted on said carrier and on the lower of said jaws forming an inner and an outer pair adapted to form 1,ase,aas

causing said outer pair of electrodes to exert a greater pressure than said inner pair of electrodes. 10

In witness whereof, I have hereunto set my hand this 19th day of October, 1923.

HENRY GEISENHONER. 

